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Thursday, January 5, 2017

The Questionable Safety of Low Cabin Pressure on Long Flights

Actress Carrie Fisher, age 60, died December 23, 2016, after experiencing a heart attack fifteen minutes before landing on an eleven-hour flight from London to Los Angeles. 

Supreme Court Justice Antonin Scalia, age 79, died of natural causes, one week following a return flight from China, on the night following another flight from Washington to Texas.

Actor James Gandolfini, age 51, died of a heart attack two days after a flight from the United States to Italy. 

My uncle, Floyd S., age 73, died of a heart attack a few days after a flight from the United States to China. 

These deaths, and others, should raise the question about whether extended air travel is safe for middle-aged or older people, who suffer from poor heart health.  The safety of extended air travel should also be examined for pregnant women or other people who may be at risk in extended periods with low oxygen.

During the 1960s, they called it “the Hawaii heart attack”.  It was common enough that it had a name.  When middle-aged or elderly couples would take a romantic, late-life trip to Hawaii, the man sometimes had a heart attack.  The heart attack usually about three to four days following arrival on the island.  My parents took a trip to Hawaii with another couple when they were in their early 50s, and the husband of the other couple had a heart attack on the third day of their trip. 

Airplane cabins are pressurized, but not to the standard atmospheric pressure at sea level.  Instead, cabins are pressurized to the air pressure equivalent to about 6500’ to 8000’ of elevation.  United States regulations require that commercial airlines pressure their cabins to an equivalent altitude of no more than 8000’.  I have no idea how well this regulation is observed or enforced.

I live in Anchorage, Alaska.  Travel to and from Alaska requires long flights, by necessity.  I have noticed variability in the physiological responses of passengers during these flights.  That variability makes me suspect that cabin pressure is not very uniform.  My wife developed altitude sickness on flights twice in the past few years, passing out on one occasion.   On other flights she has been fine.  I have also been on flights where nearly all of the passengers have fallen asleep in the middle of the day.  I don’t think this is normal, and I think it indicates insufficient oxygen in the cabin.

Anecdotal evidence is not proof.  Further, all of the people that I mention in this post had existing issues of poor health, a history of unhealthy habits, and probably engaged in unhealthy eating or drinking immediately before their heart attacks or deaths.  Nevertheless, the proximity of these heart events to long exposures to low oxygen is a reason to question the safety of low cabin pressure on long flights.  A long period of low oxygen is a reasonable explanation for a traumatic health event, through the process of stress on the heart, lungs, and blood vessels.

According to Wikipedia, many, but not all, newer models of airplane are being designed to provide a lower equivalent altitude in cabin pressure.  This suggests to me that plane manufacturers have recognized the issue.  But without a rigorous epidemiological study, the risk cannot be quantified nor appropriate standards set. 

Airplane manufactures, airlines, the FAA, the National Transportation Safety Board, and the Centers for Disease Control should all be interested in a scientific appraisal of the safety of 8000’ equivalent altitude limit.  The burden of proof should be on the airlines and airplane manufacturers to prove that this limit is safe.  Like the manufacturers of cars or electrical devices, they need to do the work which proves that their product is safe.  The study should include a statistical appraisal of heart health for older customers on long flights, and analog studies in animals to demonstrate the safety of 8000’ equivalent altitude in fetuses before birth. 


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